[leetcode] Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals[1,3],[6,9], insert and merge[2,5]in as[1,5],[6,9].

Example 2:
Given[1,2],[3,5],[6,7],[8,10],[12,16], insert and merge[4,9]in as[1,2],[3,10],[12,16].

This is because the new interval[4,9]overlaps with[3,5],[6,7],[8,10].

https://oj.leetcode.com/problems/insert-interval/

思路1：建立新的结果返回，遍历原来的线段组（注意原来是按照start排序之后的），所以根据是否和新的interval重叠，加入新的结果中（结果也要求按start排序）。

 

public class Solution {
    public ArrayList<Interval> insert(ArrayList<Interval> intervals, Interval newInterval) {
        if (newInterval == null)
            return intervals;
        ArrayList<Interval> res = new ArrayList<Interval>();

        for (Interval each : intervals) {
            if (each.end < newInterval.start)
                res.add(each);
            else if (each.start > newInterval.end) {
                res.add(newInterval);
                newInterval = each;
            } else {
                newInterval = new Interval(Math.min(each.start, newInterval.start), Math.max(each.end, newInterval.end));
            }

        }
        res.add(newInterval);

        return res;
    }

    public static void main(String[] args) {
        // Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as
        Interval one = new Interval(1, 2);
        Interval two = new Interval(3, 5);
        Interval three = new Interval(6, 7);
        Interval four = new Interval(8, 10);
        Interval five = new Interval(12, 16);
        ArrayList<Interval> intervals = new ArrayList<Interval>();
        intervals.add(one);
        intervals.add(two);
        intervals.add(three);
        intervals.add(four);
        intervals.add(five);

        System.out.println(new Solution().insert(intervals, new Interval(4, 9)));
    }

}

 

第二遍记录：

注意各种情况的处理， 最后结果也要保持原有顺序。

 

参考：

http://www.programcreek.com/2012/12/leetcode-insert-interval/

http://www.cnblogs.com/TenosDoIt/p/3715013.html